Optical trunk switches (also referred to as Optical Protection Switches (OPSs), optical switches, etc.), are all-optical devices that enable a single client (0:1) to support line-side protection (1+1, 1:1, optical ring protection, etc.). Specifically, an optical trunk switch can take a single optical channel (TX/RX) and provide it on two redundant fiber paths. These devices are designed to automatically detect traffic interruptions and quickly reroute/switch traffic from a primary fiber path to a standby fiber path. Optical trunk switches can be deployed in various scenarios, such as metro networks, Data Center interconnects, etc. Advantageously, optical switches are used to reduce client interfaces since a vast majority of faults are on the line side such as in the optical network affecting one of the lines. That is, fiber cuts or other failures in the optical network are more common than equipment failures, thus optical trunk switches provide a cost-effective approach to offer redundancy.
Also, Optical Time-Domain Reflectometer (OTDR) is a feature that is increasingly becoming commonplace in network deployments, such as integrated OTDR systems in an optical line system, i.e., integrated into modems, amplifiers, multiplexers, Reconfigurable Optical Add-Drop Multiplexers (ROADMs), etc. An OTDR provides detailed distance referenced characterization of the physical fiber plant. The OTDR generally operates by sending optical test signals into the fiber and detecting, at the same end, the scattered (Rayleigh backscatter) or reflected back light from points along the fiber. This information helps operators monitor and detect fiber span related issues, e.g., bad or poor slices, high attenuation, physical defects, etc.
At present, there is an incompatibility between optical trunk switches and OTDR based on the structure of conventional optical trunk switches. Specifically, optical trunk switches typically broadcast a transmit signal on both the primary and standby fiber and switch a received signal from only one of the primary and standby fiber. Thus, there is no conventional approach to use OTDR with an optical trunk switch to monitor both the primary and standby fibers while in-service. That is, the conventional optical trunk switch would send an OTDR test signal over both the primary and standby fibers in the transmit direction and only receive the OTDR test signal in the receive direction based on which fiber is currently active.